Extrusion of metals of hollow section



Marchfi, 1965 J. H. CAIRNS 3,172,536

EXTRUSION OF METALS OF HOLLOW SECTION Filed Oct.-l8, 1962 4 Sheets-Sheet 1 FIG. I

FIGZ

FIGS 3 2 In v 1 Z f BL- H. Cam/'71s March 9, 1965 J. H. CAIRNS 3,172,536

EXTRUSION OF METALS OF HOLLOW SECTION Filed Oct. 18, 1962 4 Sheets-Sheet 2 FIG. 4

FIG. 5

1701 17 f/- Cami/'72s EXTRUSION OF METALS OF HOLLOW SECTION Filed Oct. 18, 1962 4 Sheets-Sheet 3 FIG. 6

FIGS 3 2 I4 9 7 l3 6 l5 I77 V672 Z B VGA-r1 /7 @0775 United States Patent 7 3,172,536 EXTRUSION 0F METALS 0F HOLLOW SECTIGN John H. Cairns, Stourtou, near Leeds, England, assignor of one-half to Yorkshire Imperial Metals Limited, near Leeds, England, a company of Great Britain Filed Oct. 18, 1962, Ser. No. 231,394 Claims priority, application Great Britain, Get. 20, 196i, 37,681/ 61 1 Claim. (Cl. 72-22) This invention relates to the extrusion of metals of hollow section.

In extrusion, where a solid billet is being used to produce a tubular shell, a mandrel is normally pushed through the centre of the billet, but difficulties arise in this connection and it is the object of this invention to provide a new method of extruding when a mandrel is being used in this way, and to provide a new form of mandrel for such purposes.

The process of extruding metals of hollow section in accordance with this invention comprises pushing a mandrel through the centre of the billet whilst forcing a stream of lubricant between the mandrel and the billet.

Preferably the stream of lubricants is fed through the approximate centre of the mandrel and out to the periphery of the mandrel at or near the tip.

An improved mandrel made in accordance with this invention is therefore characterised by the provision of a channel for lubricant passing through or near the centre of the mandrel and outwards to the periphery near the tip.

The scope of the monopoly is defined by the appended claim; and how the invention can be performed is hereinafter particularly described with reference to the accompanying drawings in which:

FIGURE 1 is a longitudinal section of parts of an extrusion press of usual type shown part way through a piercing operation;

FIGURE 2 is a view similar to FIGURE 1 but at the end of a piercing operation;

FIGURE 3 is a similar view of the parts just after extrusion has started;

FIGURE 4 is a view in longitudinal section of an arrangement according to the invention for supplying a lubricant to the newly formed internal surface of a billet during the piercing operation;

FIGURE 5 is a perspective view of a mandrel nose which may be employed in the present invention;

FIGURE 6 is a view similar to FIGURE 4 showing the parts partway through the piercing operation;

FIGURE 7 is a similar view at the end of the piercing operation;

FIGURE 8 is a similar view just after extrusion has started; and

FIGURE 9 is a diagrammatic representation of the lubricating and cooling system applied to the extrusion mandrel.

Like references refer to like parts throughout the drawings, where 1 denotes a billet which is to be extruded in hollow section, 2 the liner of an extrusion pTess, 3 the container, 4 the die holder, 5 the die, 7 the mandrel, 8 the stem and 9 the pressure disc.

FIGURES l, 2 and 3 illustrate the origin of the eccentricity which is commonly experienced in tubes or hollow sections extruded by conventional methods. The

3,172,536 Patented Mar. 9, 1965 eccentricity originates at the piercing stage and is influenced amongst other things, by incorrect adjustment of the press and wear on moving parts, etc. Consequently during piercing, the mandrel 7 does not travel through the exact central axis of the billet 1 and at the end of piercing the central axis of the mandrel 7 is not infrequently quite dilferent from the central axis of the billet l, as shown in FIGURE. 2. Consequently at the beginning of extrusion, the wall thickness of the extruded product 10 is non-uniform as shown in FIGURE 3 where the wall thickness of the extruded shell 10 is greater at the top than at the bottom.

FIGURE 4 illustrates the arrangement for introducing a supply of lubricant through a hollow mandrel 7 which emerges via grooves 14, 15 respectively along the spigot 16 and back face of an oversize nose 6. The spigot 16 fits into a bore 12 formed in the end of the mandrel 7. The lubricant then flows along an annular gap 11 between the billet 1 and the mandrel 7, and forms a lubricating layer between the outer surface of the mandrel 7 and the newly formed inner surface of the billet 1.

The grooves 14 and 15 are more clearly seen in the perspective view of the nose 6 in FIGURE 5. The lubricant may be solid, liquid or gaseous, or a combination of these.

Whilst many lubricants are possible it has been found that with some metals a controlled oxidation of the bore by a suitable medium, e.g., air, introduced as described, can provide a high degree of lubrication very simply and economically. Similarly, controlled oxidation of or similar chemical reaction with other surfaces provides a similarly eifective lubrication.

FIGURES 6, 7 and 8 illustrate how the oversize mandrel nose 6, which at the extrusion temperature is a sliding fit in the die 5, considerably reduces, or eliminates the eccentricity of the extruded product. FIGURE 6 shows the mandrel 7 partway through the piercing operation. The mandrel 7 has deviated from the central axis of the billet 1 by an amount equal to that shown in the known arrangement of FIGURE 1. FIGURE 7 shows the position at the end of the piercing operation where the oversize mandrel nose 6, which as stated above, is a sliding fit in the die 5, has realigned the mandrel along the central axis of the billet 1. The annular gap 11 between the mandrel 7 and the billet 1 allows the realignment of the mandrel 7 to take place without bending the mandrel. This can be seen clearly in FIGURE 7 where the annular gap 11 at the end of the piercing operation is no longer symmetrical with respect to the realigned mandrel 7. When the pressure is applied to the main ram at the end of the piercing operation the annular gap closes up and extrusion commences with the mandrel 7 in the central axis of the billet 1 as shown in FIGURE 8. The oversize nose 6 is lifted off the mandrel 7 by the front end of the extruding shell 10.

FIGURE 9 shows in diagrammatic form the lubricating and cooling system applied to the mandrel. Referring to this figure, the extruding press comprises a hydraulic cylinder 17 containing a ram 18 by which the piercing and extrusion pressure is applied. Fixed to the outer end of the ram 18 is a crosshead 19 which carries a cam 20. Placed at appropriate intervals along the stroke of the crosshead are three limit switches, respectively 21, 22 and 23, whose plungers are actuated in turn by the cam 20 in the course of the stroke of the ram 18. The

3 electrical control will be referred to more particularly later.

Fixed in the end of the crosshead 19 is a piercer stem 24, which carries the mandrel 11, and which contains a bore 25 containing a centrally located tube 26. The bore 25 communicates with a transverse bore having a connection 27 from which a pipe 28 leads to a first solenoid valve 29. The solenoid valve 29 is of a conventional type containing an electromagnet winding which, when energized, moves the valve to an open position, the valve being returned to its closed position by a spring when the winding is tie-energized. From the solenoid valve 29 a pipe 30 leads to a lubricant pump 31, which needs no further descripiton since any suitable kind of pump such as a geared pump, an impeller pump er a piston pump may be used. From the central tube 26 a transverse tube leads to a connection 32 from which a pipe 33 leads to a second solenoid valve 34, which is of the same type as the valve 29.. From the second solenoid valve 34 a pipe 35 leads to a coolant pump 36 which may also beof a conventional type and requires no further description. The lubricant pump 31 draws lubricant via a pipe 37 from a lubricant tank 38 while a coolant pump 30 draws coolant via a pipe 39 from a coolant tank 40.

A non-return valve or check valve 41 is provided at the endsof the bore 25, the tube 26 passing through this valve, and at the end of the tube itself a second nonreturn or check valve 42 is provided. The check valve 41 prevents coolant under pressure from being forced into the lubricant bore 25, and the check valve 42 prevents lubricant under pressure from being forced into coolant tube 26 Returning now to the electrical circuitry, there are several ways of [arranging the switching which will occur to persons skilled in the art, but one efiiective method isillustrated. The limit switch 21 is a changeover switch which has a moving contact which, in its two positions, connects the live electric .mains line 43 to one or other of two fixed contacts. It has a spring loaded operating plunger which is engaged by the cam 20 and each time the plunger is pressed in and released the moving contact changes from one fixed contact to the other. The

limit switch 22 is of a similar type to the switch 21 insofar as its actuation is concerned, but it is a double changeover switch, that is to say, it contains two separate changeover switches both actuated by the one plunger. The limit switch 23 may be of the same type as the limit switch 21. The two fixed contacts of the limit switch 21 are connected by lines 44 to one pair of .fixed contacts in the switch 22 and the associated moving contact is connected by a line 45 to the first solenoid valve 29;. The second moving contact in the switch 22 is connected to the main supply line 43 and the associated fixed contacts are connected by lines 45 to t shown, which is a withdrawn position, and the .cam 20 is ,in the rearward position shown with respect to the switches 21, 22 and 23. placed in the die chamber or liner, hydraulic pressure is applied'to the cylinder 17 and the ram 18 begins to move forward, carrying the crosshead 19, the piercer stem 24 and the mandrel 11 forward. When the nose piece 6 reaches the billet at the commencement of the piercing operation, the cam 20 reaches the position shown dotted at 47 to engage the plunger of the switch 21 and actuate the switch. The changing over of the contacts in this switch energizes the first solenoid valve 29, which is opened so that lubricant is supplied through the pipe After va hot billet has been 28 to the bore 25, through the valve 41 and through the bore 13 in the mandrel, to provide lubrication during the piercing operation. When the piercing operation has been completed the cam 24) reaches the position shown dotted at 48 to actuate the plunger of the switch 22 and change over both sets of contacts. The change of one set of contacts breaks the supply over the line 45 and deenergizes the solenoid valve 29, which immediately closes. At the same instant, the change of the other pair of contacts energizes the second solenoid valve 34 over the line 46, so that this valve is opened and a supply of coolant flows through the pipe 33, the tube 26, the non-return valve 42 and the bore 13 'to the interior of the extrusion. It will be recalled from the earlier descriptionthat when'actual extrusion commences the nose piece 6 is pushed off the end of the mandrel and merely falls into a suitable receptacle, so that the coolant may flow freely through the bore 13 and thence into the bore in the extrusion to cool it. At the end of the extrusion stroke the cam 29 reaches the position shown dotted at 49 to actuate the switch 23. The changing over of its contacts de-energizes the solenoid valve 34 so that this valve closes and cuts off the coolant supply.

In the case of the extrusion of copper or copper base alloys the coolant may comprise water or a dilute solution of soluble oil in water.

Extrusion by the process hereinbefore described and using a mandrel in accordance with this invention will permit a greater extrusion ratio than is normally possible.

Additional advantages believed to result from the use of this invention are:

(a) Reduced frictional resistance between the mandrel and'the billet during subsequent extrusion which reduces the required extrusion pressure, thus permitting more eflicientuse of the press, e.g., by using larger billets or high extrusion ratios.

(/5) Promotion of uniform flow of metal during extrusion which prevents the. formation of extrusion defects that could otherwise occur under non-lubricated now conditions.

(0) Reduced heat transfer from the billet to the mandrel during extrusion due to the lubricant film acting as a thermal barrier.

(d) Reduced frictional heating of the mandrel during extrusion and reduced tensile pull on the mandrel during extrusion, giving better tool life.

(e) Improved mandrel coolingthe coolant which is forced throughthe. mandrel during=the extrusion period absorbs much of the heat that is conducted to the mandrel from the hot billet, thereby preventing overheating of the mandrel.

(f) Avoidance of bore contamination by atmospheric gases-the stream of coolant that emerges from the front end of the mandrel into the bore of the extruded product immediately vapouriscs and the copious quantities of vapour so formed prevent the ingress of atmospheric oxygen or nitrogen to the bore of the extruded product, and this prevents the formation of undesirable 'films of oxide or nitride on the bore surface.

(g) Improved product cooling-the stream of coolant which emerges from the hollow mandrel during extrusion causes the extruded product to cool more rapidly than would be the case with normal extrusion practice, this is particularly desirable for some metals and alloys.

The invention is not limited by the foregoing details which are given by way of example, as various modifications may be made to suit requirements.

What is claimed is:

In an extrusion press for the extrusion of copper and copper base alloys of hollow section, a diehead and a die, a. container for a billet, a pressure disc, an extrusion ram, a piercing mandrel having an approximately central bore extending through its length, a nose for said mandrel having a spigot fitting into said bore at the end of the mandrel remote from said operating ram, grooves in the surface of said nose on said spigot and on the rear face of the nose, said nose being a sliding fit in said die at working temperature of said press, means for supplying lubricant under pressure to said bore, an electrically operated solenoid valve controlling said lubricant supply, means for supplying coolant under pressure to said bore, an electrically operated solenoid valve controlling said coolant supply, limit switches controlled by the piercing mm :at the limiting positions of its stroke, limit switches controlled by the extrusion ram at the limiting positions of its stroke, said limit switches controlling said solenoid valves to supply lubricant to said bore during the piercing of a billet, to stop the supply of lubricant at the end of a piercing ope-ration, to start the supply of coolant to said bore at the commencement of an ex- 15 trusion stroke and to terminate the supply of coolant to said bore at the end of the extrusion stroke.

References Cited by the Examiner UNITED STATES PATENTS Robertson 2073 Swift et a1 20719 Staples 20710.1 Griley 20710 Roux 789 Sejournet 207-10.1 Kreidler 2079 Mulrooney 2079 Arenz 2073 Billen et a1. 2073 Arenz 20716 Karnie 20710 MICHAEL V. BRINDISI, Primary Examiner. CHARLES W. LANHAM, Examiner. 

